Source: http://feedproxy.google.com/~r/OfficialGmailBlog/~3/c0qraShf18E/unsubscribing-made-easy.html
Posted by Brad Taylor, Gmail Spam CzarWe believe you should only get the mail you want to get. Some of you already use the "Report Spam" button on all kinds of unwanted email, and for that we're very thankful: the more spam you mark, the better our system gets at weeding out junk mail.
Unsubscribing from mailing lists and newsletters you subscribed to a while back but no longer want to receive should be just as easy. Searching through individual messages for little unsubscribe links is too big a pain —you should be able to unsubscribe with a single click.
So we just launched something that makes this all work better, both for Gmail users and big email senders. Now, when you report spam on a legitimate newsletter or mailing list, we'll help you unsubscribe. After clicking report spam, you'll see a little dialog like this:
Clicking "Unsubscribe" will automatically send a request back to the sender so they'll stop emailing you.
This only works for some senders right now. We're actively encouraging senders to support auto-unsubscribe — we think 100% should. We won't provide the unsubscribe option on messages from spammers: we can't trust that they'll actually unsubscribe you, and they might even send you more spam. So you'll only see the unsubscribe option for senders that we're pretty sure are not spammers and will actually honor your unsubscribe request. We're being pretty conservative about which senders to trust in the beginning; over time, we hope to offer the ability to unsu! bscribe from more email.
For those of you senders who are interested in this feature, the most basic requirements are including a standard "List-Unsubscribe" header in your email with a "mailto" URL and, of course, honoring requests from users wishing to unsubscribe. You'll also need to follow good sending practices, which in a nutshell means not sending unwanted email (see our bulk sending guidelines for more information).
With an easy way to unsubscribe, everybody wins. Your spam folder is smaller, and senders don't waste time sending you email that you no longer want.
Update (1:50pm): If you want to unsubscribe without reporting the message as spam, click "show details" in the top-right corner of the message, then click "Unsubscribe from this sender."